Individual battery cells, accumulator cells or fuel-cell cells are usually interconnected to form packs and modules in order to achieve the capacitances and voltages required by the target application. Depending on the form of the contact points of the cells, the contacting is accomplished either integrally by soldering or welding, or with form locking and/or force locking by wiring, clamping or screw-coupling of the contacts.
One major challenge lies in ensuring a constantly high current-carrying capacity and a constantly low contact resistance between the cell and the contacting device during operation and over the entire operating time. Temperature fluctuations, effects of moisture and external mechanical stresses such as vibrations during the operating time may weaken the contacting and lead to an increase in contact resistance, and therefore to a decrease in battery performance.
Material-locking contactings make it possible to achieve very low contact resistance, however, replacement of individual defective cells is associated with considerable expenditure.
It may be that force-locking and/or form-locking contactings make it easy to replace individual cells due to releasable contactings; however, conventional contact materials such as metallic copper, aluminum, silver or gold may exhibit creep effects under mechanical strain, e.g., due to a clamping connection or screw connection, with the result that the contact resistance at the contact point increases with time. In particular, elevated temperatures which may be present when used in automobiles, for example, may accelerate the creep effects considerably. If, besides elevated temperatures, the effects of moisture also occur, this may lead to corrosion of the contact points and therefore to a further increase in the contact resistance.